Experiments were carried out in Syria with parathion dusts for the control of Eurygaster integriceps Put. on wheat to ascertain the best time to apply the dust and the most suitable rate of application using a 6 h.p. dusting machine mounted on a “ jeep ”.
A field experiment is described in which a dust containing 0·75 per cent. parathion was applied under a drag-sheet to three plots of wheat at rates of 40, 20 and 10 kg. per hectare, respectively. The insects onthe wheat were mostly in the first three instars and the population was assessed by making 100 hand sweeps with a net at both 60 hours and 70 hours after treatment on each plot. The effect of treatment when compared with a control plot was to reduce the insect population in the three plots by 98·4 per cent., 83 per cent. and 65 per cent., respectively.
A further field experiment on a larger scale was carried out in an area in which plots of wheat were interplanted with plots of barley. In this case, the great majority of the insects were fourth-stage nymphs or adults. Five plots of wheat were treated with a dust containing 0·8 per cent. parathion at a rate of 35 kg. per hectare without using a drag-sheet. In two of the plots which were dusted in calm weather, about 89 per cent. control was obtained, in the other plots the effectiveness of the dusting was appreciably reduced by wind.
A cage containing 1,406 live specimens was placed, prior to dusting, in one of the plots of the latter experiment (dusted under calm conditions) and 6¾ hours after treatment all were dead. In the control only two specimens out of a total of 239 originally caged were found dead 24 hours later.